A passenger compartment of a vehicle is typically heated and cooled by a heating, ventilating, and air conditioning (HVAC) system. The HVAC system directs a flow of air through a heat exchanger to heat or cool the air prior to flowing into the passenger compartment. In the heat exchanger, energy is transferred between the air and a coolant such as a water-glycol coolant, for example. The air is normally supplied from ambient air or a mixture of air re-circulated from the passenger compartment and the ambient air.
One of the objectives of the HVAC system is to make occupants within the passenger compartment comfortable. As such, the HVAC system typically includes one or more zones controlled by climate system settings (e.g. a temperature setting) established by the occupants. A control algorithm of the HVAC system determines adjustments to a temperature, a volume, and a rate of air flowing into each of the zones in accordance with the climate system settings established by the occupant located therein. A drawback of the control algorithm is that the climate system settings of prior occupants govern the HVAC system which may be counterproductive. For example, the settings of the prior occupants may require a heating of a respective zone when a cooling of the zone is desired. Further, if one of the zones is unoccupied, the climate system settings for the zone may affect the comfort of occupants in other zones.
Accordingly, it is important that the control algorithm of the HVAC system can also determine occupant comfort. Occupant comfort, however, is a complex reaction, involving physical, biological, and psychological responses to external conditions. Because of the complexity, the control algorithm of the HVAC system must consider variables that affect occupant comfort and a relationship between those variables and actual occupant comfort. Current HVAC systems employ multiple sensors and control actuators to measure and control the variables that affect occupant comfort. A typical HVAC system may include a temperature sensor measuring a temperature inside the passenger compartment, another temperature sensor measuring a temperature of the ambient air, and other additional sensors measuring sun heating load, humidity, etc. The control actuators of the HVAC system may include a variable speed blower, a means for varying the temperature and a direction of the air flow, as well as a means to control the mixture of air re-circulated from the passenger compartment and provided from the ambient air. The current HVAC systems, however, do not include algorithms that translate HVAC system measurements to occupant comfort. Further, current HVAC systems have a relatively large package size and consume a significant amount of energy. Recently, demand for reduced vehicle energy consumption, especially for hybrid and electric vehicles, has resulted in an effort to reduce energy requirements of the HVAC system.
Thus, there exists a need for a vehicle climate control system and a method of controlling the vehicle climate control system, which minimizes energy consumption, a package size, and a cost thereof, while maximizing occupant comfort.